Product and method of making fused litharge particles coated with red lead



M. F. CHUBB 48,353 PRODUCT AND METHOD OF MAKING FUSED LITHARGE PARTICLES COATED WITH RED LEAD Filed Oct. 4, 1944 I N VEN TOR.

& MELVlN F. CHUBB Patented Aug. 31, 1948 PRODUCT AND T'METHOD OF -MAKING'FUSED LITHARGE-PARTICLES COATED WITHRED f LEAD Melvin .F. Chubb, Joplin, Ma, assignorn to, The Eagle-Picher Company, Cincinnati; Ohio; a cor poration of Ohio Application October 4, 1944,-=Serial No.2557,146-- 11 Claims.

This invention relates to. a fused litharge, each particleof which hasa coatingsof red: lead. This product -.is .:particularly 1 useful :irr'thet positive platesvof storage batteriesyand itsuse'in such connect-ion'ha's been disclosed in co-pendingapplication Serial No. 523,934 made by one: of. the present inventors, Melvin F. Chubb, together with H'e'rshel/Briggs; When properly used, it confers the advantages of fast formation which may take Inthe drawings,

Figure 1 is a longitudinal sectional view of the apparatus.-.

Figure 2 is'a cross section taken on the line 2- .-2 of Figure l.

Figure3 is a cross section taken on the line 3-3 of Figural.

I is:a rotary kiln= of the inclined cylinder type; A cylinder 1 l is mounted upon piers l2 upon plac'e in acid trong enough to be used in the which there. are rollers I3- over which large beartery itself'when the latter is in service. A longer mg rings revolve The latter encircle battery"lite results because the paste does not A lining refractory brick is P slough off the plates in service; This effect leads At the higher end of Cylinder I I is a breechmg to much longer bench or cycling life test-h l 6 closing the-otherwiseopen end of the cylinder Briefiystated, the invention-first comprises the and providing a draft through a stack A preparationof a fu d lithargvwhich may door I8 is provided asa clean-out near the bottom either of the-red or yellow modification. Follow- Ofthe breaching? The kiln 1S f throPgh hopJ ingthe preparation thereof, a coatingofred lead 'per:l9 and a flow tube I911, which consists prefer-t P5304; generated on the part-[mesv of the 1ith ably of a .dellvery or-inn'er tube and an outerior protective tube so thatblows will not construct arge b oxidizing the latter in a suitable kiln "or furnace ata temperature of about 800 F."to'950 F. with free-access of air. From 15 to 50% preferably about by weight of" Pb304, is then burnt-in during the oxidation step.

Themanufacture. of fused litharge is per se not new. A complete disclosure of how it is made forms the subject matter-of U. S. Patent 592,594, October 26, 1897 to Carl V. Petraeus. It may be mentioned, however, that the yellow modification is made by allowing the fused litharge to cool rapidly as for instance by falling on a concrete or iron'floor which is at ordinary temperature. Ifithe stream of molten litharge is allowedto flow into an iron pot, say of five to one hundred-or more gallons capacity,itwill-coolslowly and the reddish modification will be formed.

The IediOI' yellow cooled product is now ground in a micromill ofthe Bird or theR'aymond types, or of the swinghammeror ball mill type, preferably with air separation, or other suitable milLto a particle size rangin'gfrom 3 to 6 microns radius. The ground product is now charged into a kiln which may be. the one which is illustrated-in the figurabut which may also be'zof the older type employing a round basin. and. a rabble. arm." The kiln is operated, as before stated, at between:

800 F. and 950 F. under conditions of free access of air and continuous agitation b rotation. The air blast must not be so strong as to blow particles of the product out of the kiln. When using the latter, production is continuous, the speed of rotation of the kiln being adjusted to the speed with which the product is formed.

the. feed channel.

At the: opposite lower end-of cylinder l I there isza removable bree'ching 20 through the vertical wall 2 t of which. there projects a gas oroil burner 22. As sh'own in dottedline', it may be rolled'b'ack on'wheels, leaving the delivery spout23 whi'chor-s.

dinarilyprojects downward from it through the floor'in place;

Belowthefloor level-there is a rotary, prefer ably polygonalscreen drum 24, somewhatinclined in the samedirection as the kiln. By reason'of such inclination, a continuous gravity-induced travel of the -materia1 to be heated occurs throughout the entire apparatus. Drum- 24 is supported on the high end by a hub 25 and a hanger=26 supporting the hub and affording a bearing surfacefor its rotation. The low'end is supported by a spider 21, the 'hub ofwhich is tightto a drive shaft 28 and the' outer ends of which are encircled by arim 29to which the'drum is fast; A hanger 30- supports the drive "shaft.

Spam-fingthe lower part of the drum is. a hopper housing 3 ltoicatch the flue material" passing the sieves;

The" apparatus" isoberatdlike any standard.

per minute the kiln should make, since time of retention is the controlling factor. In general, the heating at the temperature range specified should last for a period between 30 minutes and 6 hours. The longer times are necessary when the older type of rabbled batch furnace, previously mentioned, is employed. The flame employed in kiln operation should be short and supplied with sufli'cient oxygen for complete combustion. It should not touch the material to be oxidized.

The process up to this point is identical for two variations of the product that are commercially valuable. The first of these products is screened but not milled after it leaves the kiln cylinder l I. It is called A for convenience. The second product is not customarily screened but is dry-milled in an impact pulverizer or similar mill in order to crack the particles. It is called B.

Product A is intended for use in a battery paste prepared according to the eo-pending application of M. CE. Chubb, Serial No. 551,000. In the application referred to, product A is mixed with basic or normal lead sulfate, the mixture moistened and packed into storage battery grids where it then hardens. In order that a reasonable time interval may elapse between the moistening and the hardening, product A is" made to be slow acting. Consequently, very small sized particles are not desired since the smaller the particle the faster the reaction. Exposure of the litharge also apparently hastens the reaction, so no efiort is made to crack the particles or otherwise expose the litharge such as is the case in making product B. Product A should range from 3 to 6 microns median radius.

Product B is, as previously mentioned, prepared usually without screening, but with thorough milling in an impact or other pulverizer to a median radius of particle of 1.5 to 4 microns. Substantially each particle is split so as to expose a surface both of litharge and red lead. For this reason, the reaction rate, with normal sulfuric acid, is rapid. It is intended for use in making the paste used in the positive plates of storage batteries, particularly as disclosed in pending application Serial No. 523,934 of Chubb and Briggs mentioned in the introduction to this specification. For some reason, not yet understood, the plate made with a paste formed from this material can be over-formed or given excess charging current on the initial conversion to lead peroxide over and above that required to convert the materials to lead peroxide without damage to the plate.

The invention described herein is referred to in my copending applications Serial Nos. 523,933, 540,668 and 563,274, and in the copending applications of myself and Briggs, Serial No. 523,934 and of myself and Hense, Serial No. 551,000.

Iclaimas my invention: i I

1. A lead oxide product useful for making a paste for storage battery plates which comprises split particles, which consisted, before splitting, of a core of fused litharge coated with Pba04, said Pbs04 weighing from to 50% of the entire mass, said split particles ranging in median radius from approximately 1.5 to 4 microns.

' 2. A battery oxide consisting essentially of particles ranging in median radius from approximately 3 to 6 microns, said particles having a core of fused litharge and said particles havin; a coating of P191504.

3. A lead oxide product useful for making 2 paste for storage battery plates which comprise: split particles, which consisted, before splitting of a core of fused litharge coated with PbaO-i, saic split particles ranging in median radius from approximately 1.5 to 4 microns.

4. A product according to claim 1 in which the core is red litharge.

5. A .product according to claim 1 in which the core is yellow litharge.

6. The process of making a lead oxide produci suitable for use in making paste for storage battery plates, which comprises oxidizing lead tc litharge above the fusion point but below the volatilization point of the litharge, cooling and milling said litharge, preheating it with free access of air to a temperature ranging from about 800 F. to 1000 F. until it acquires a coating of Pb3O4 weighing between 15% and 50% of the entire mass, then milling the product so obtained to split the particles thereof and to produce particles having a median radius ranging from 1.5 to 4 microns.

7. A process according to claim 6 in which the cooling is sufficiently rapid to form yellow litharge.

8. A process according to claim 6 in which the cooling is sufiiciently slow to form red litharge.

9. The process of making a product useful in storage battery positive plates which comprises fusing litharge, grinding the fused, cooled product to a fineness between 3 and 6 microns median radius, then heating the ground product to about 800 F. to 1000 F. with free access of air for a time ranging from 30 minutes to 6 hours, cooling and screening the product to a fineness of 3.0 to 6 microns.

10. Aprocess according to claim 9 in which the litharge is the yellow modification.

11. A process according to claim 9 in which the litharge is the red modification.

MELVIN F. CHUBB.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 592,594 Petraeus Oct. 26, 1897 637,028 Petraeus Nov. 4, 1899 1,491,237 Hufford et al Apr. 22, 1924 1,992,395 Rose et a1 Feb. 26, 1935 2,182,436 Johnstone Dec. 5, 1939 2,235,487 Mayer Mar. 18, 1941 OTHER REFERENCES M'attrello, Protective and Decorative Coatings, vol. II, pp. 358, 359 and 361 (1942), John Wiley & Sons, N. Y.

Transactions Aime, vol. 128, pages 37-41, 56.

Mellor, Comprehensive Treatise on Inorganic and Theoretical Chemistry, 1927, vol. 7, page 644, Sec. 13. 

